1. Field of the Invention
The present invention relates to an improvement of a method of sealing an electronic component with molded resin for sealing an electronic component such as an IC, an LSI, a diode, a capacitor or the like which is mounted on a lead frame with a resin material.
2. Description of the Background Art
In general, an electronic component is sealed with molded resin by transfer molding. In general, this method is carried out through a mold assembly for sealing an electronic component with resin as follows:
A fixed upper mold section and a movable lower mold section of the mold assembly are previously heated to a resin molding temperature with heating means, and the upper and lower mold sections are opened.
Then, a lead frame provided with an electronic component is supplied to/set on a prescribed position of a mold surface of the lower mold section, while a resin material is supplied into pots of the lower mold section.
Then, the lower mold section is upwardly moved to close the upper and lower mold sections. At this time, the electronic component and the lead frame around the same are engaged and set in upper and lower mold cavities which are oppositely provided on the mold surfaces of the upper and lower mold sections respectively, while the resin material received in the pots is heated and successively melted.
Then, the resin material heated/melted in the pots is pressed with plungers to be injected into and charged in the upper and lower mold cavities through resin passages, whereby the electronic component and the lead frame around the same received in the mold cavities are sealed in a resin mold package which is molded in correspondence to the shapes of the mold cavities.
After a lapse of a time which is necessary for hardening the melted resin material, the upper and lower mold sections are opened so that the resin mold package and the lead frame in the upper and lower mold cavities and the hardened resin in the resin passages are released from the mold assembly with ejector pins provided on the mold sections respectively.
Although the heated/melted resin material is injected into and charged in the mold cavities and a prescribed resin pressure (resin pressing force) is applied to the resin injected into and charged in the mold cavities with the plungers, however, adhesion (adhesiveness) between the resin mold package molded in the mold cavities and the lead frame is so weak that a clearance is disadvantageously readily defined between the resin mold package and the lead frame.
Namely, water infiltrates from the clearance and inhibits the function of the electronic component sealed in the resin mold package, to disadvantageously deteriorate the quality of the product (resin mold package) and damage its reliability.